Donald Trump Jr ventured on to the University of California’s overwhelmingly liberal Los Angeles campus on Sunday, hoping to prove what he had just argued in his book – that a hate-filled American left was hell-bent on silencing him and anyone else who supported the Trump presidency.

But the appearance backfired when his own supporters, diehard Make America Great Again conservatives, raised their voices most loudly in protest and ended up drowning him out barely 20 minutes into an event scheduled to last two hours.

The audience was angry that Trump Jr and his girlfriend, Kimberly Guilfoyle, would not take questions. The loud shouts of “USA! USA!” that greeted Trump when he first appeared on the stage of a university lecture hall to promote his book Triggered: How The Left Thrives on Hate and Wants to Silence Us quickly morphed into even louder, openly hostile chants of “Q and A! Q and A!”

The 450-strong audience had just been told they would not be allowed to ask questions, “due to time constraints”.

At first, Trump and Guilfoyle tried to ignore the discontent, which originated with a fringe group of America Firsters who believe the Trump administration has been taken captive by a cabal of internationalists, free-traders, and apologists for mass immigration.

When the shouting would not subside, Trump Jr tried – and failed – to argue that taking questions from the floor risked creating soundbites that leftwing social media posters would abuse and distort. Nobody was buying that.

In minutes, the entire argument put forward by the president’s son – that he was willing to engage in dialogue but that it was the left that refused to tolerate free speech – crumbled.

“I’m willing to listen…” Trump began.

“Q and A! Q and A!” the audience yelled back.

“We’ll go into the lion’s den and talk …” Trump tried again.

“Then open the Q and A!” came the immediate response.

Guilfoyle, forced to shout to make herself heard, told students in the crowd: “You’re not making your parents proud by being rude and disruptive.”

She and Trump Jr left the stage moments later.

The fiasco pointed to a factional rift on the Trump-supporting conservative right that has been growing rapidly in recent weeks, particularly among “zoomers” – student-age activists. On one side are one of the sponsors of Trump Jr’s book tour, Turning Point USA, a campus conservative group with a track record of bringing provocative rightwing speakers to liberal universities.

On the other side are far-right activists – often referred to as white supremacists and neo-Nazis, although many of them reject such labels – who believe in slamming the door on all immigrants, not just those who cross the border without documents, and who want an end to America’s military and diplomatic engagement with the wider world.

A number of the loudest voices at Sunday’s event were supporters of Nick Fuentes, a 21-year-old activist with a podcast called America First that has taken particular aim at Turning Point USA and its 25-year-old founder, Charlie Kirk. In a number of his own recent campus appearances, Kirk has faced questions accusing him of being more interested in supporting Israel than in putting America first. He has responded by calling his detractors conspiracists and racists.

On Sunday, Kirk appeared alongside Trump Jr. and Guilfoyle but said nothing.

Two Fuentes supporters, delighted with the outcome of Trump Jr’s appearance, later told the Guardian the pro-Trump movement was being infected with “fake conservatism” and that the president himself was at the mercy of a cabal of deep state operatives who wouldn’t let him do many of the things he campaigned on.

The pair, who called themselves Joe and Orion Miles, said: “It was an absolute disaster for them. We wanted to ask questions about immigration and about Christianity, but they didn’t want to face those questions.”

Also, if Trump Jr was expecting a small army of “triggered” leftwingers to clamour for his silence, he did not get it. No more than 35 protesters showed up and, despite making a lot of noise with drums and whistles and shouts of “Trump-Pence Out Now!”, resisted taunts and insults from provocateurs in Make America Great Again hats from across a line of metal barriers.